diff --git a/tools/build-benchmark.cmd b/tools/build-benchmark.cmd
index 39b9f180d9..379cb1313a 100644
--- a/tools/build-benchmark.cmd
+++ b/tools/build-benchmark.cmd
@@ -1,5 +1,5 @@
 @echo off
-set VS_TOOLS_VERSION=vs2019
+set BUILDTOOLS_VERSION=vs2019
 set CMAKE_GEN="Visual Studio 16 2019"
 echo Building Google Benchmark (test only dependency)...
 @setlocal ENABLEEXTENSIONS
diff --git a/tools/build-clang-12.cmd b/tools/build-clang-12.cmd
new file mode 100644
index 0000000000..a41c5bb6c1
--- /dev/null
+++ b/tools/build-clang-12.cmd
@@ -0,0 +1,7 @@
+@echo off
+pushd %~dp0
+set "PATH=%ProgramFiles%\LLVM-12\bin;%PATH%"
+set BUILDTOOLS_VERSION=clang-12
+set CMAKE_GEN=Ninja
+call build.cmd %*
+popd
diff --git a/tools/build-clang.cmd b/tools/build-clang.cmd
new file mode 100644
index 0000000000..c160fd661b
--- /dev/null
+++ b/tools/build-clang.cmd
@@ -0,0 +1,7 @@
+@echo off
+pushd %~dp0
+set "PATH=%ProgramFiles%\LLVM\bin;%PATH%"
+set BUILDTOOLS_VERSION=clang
+set CMAKE_GEN=Ninja
+call build.cmd %*
+popd
diff --git a/tools/build-vs2015.cmd b/tools/build-vs2015.cmd
index 30bb41c3c9..ed230d1559 100644
--- a/tools/build-vs2015.cmd
+++ b/tools/build-vs2015.cmd
@@ -1,11 +1,33 @@
 REM Build with Visual Studio 2015
-set "VS_TOOLS_VERSION=vs2015"
-set ARCH=Win64
+set "PATH=%ProgramFiles(x86)%\MSBuild\14.0\Bin;%ProgramFiles(x86)%\Microsoft Visual Studio 14.0\VC\bin;%PATH%"
+
+REM ### Note that vcpkg built with 2019/2017 can't be used with 2015!
+REM ### Consider to specify custom VCPKG_ROOT for 2015 as follows:
+REM
+REM set VCPKG_ROOT=C:\vcpkg.2015
+REM
+
+set BUILDTOOLS_VERSION=vs2015
+set ARCH=x64
 if NOT "%1"=="" (
   set ARCH=%1
 )
-set "CMAKE_GEN=Visual Studio 14 2015 %ARCH%"
+set "CMAKE_GEN=Ninja"
+set "VCPKG_VISUAL_STUDIO_PATH=%ProgramFiles(x86)%\Microsoft Visual Studio 14.0"
+
+REM Building with Windows SDK 8.1
+set "PATH=%ProgramFiles(x86)%\Windows Kits\8.1\bin\%ARCH%;%PATH%"
+set WINSDK_VERSION=8.1
+set CMAKE_SYSTEM_VERSION=8.1
+set VCPKG_PLATFORM_TOOLSET=v140
+
+REM ### Replace above Windows SDK 8.1 by Windows 10 SDK if necessary.
+REM ### Resulting binaries may not be compatible with Windows 8
+REM
+REM set WINSDK_VERSION=10.0.19041.0
+REM set "PATH=%ProgramFiles(x86)%\Windows Kits\10\bin\10.0.19041.0\%ARCH%\;%PATH%"
+REM
+
 cd %~dp0
 call setup-buildtools.cmd
-REM TODO: currently we cannot build without Abseil variant for Visual Studio 2015
-call build.cmd -DWITH_ABSEIL:BOOL=ON
+call build.cmd -DMSVC_TOOLSET_VERSION=140
diff --git a/tools/build-vs2017.cmd b/tools/build-vs2017.cmd
index de84593123..3a95d9b110 100644
--- a/tools/build-vs2017.cmd
+++ b/tools/build-vs2017.cmd
@@ -1,10 +1,17 @@
 REM Build with Visual Studio 2017
-set "VS_TOOLS_VERSION=vs2017"
-set ARCH=Win64
+set "BUILDTOOLS_VERSION=vs2017"
+set ARCH=x64
 if NOT "%1"=="" (
   set ARCH=%1
 )
-set "CMAKE_GEN=Visual Studio 15 2017 %ARCH%"
+
+REM ### Uncomment below to use Visual Studio MSBuild solution.
+REM ### Ninja generator produces much faster builds. But it is
+REM ### easier to debug MSBuild solution in vs2017 IDE :
+REM
+REM set "CMAKE_GEN=Visual Studio 15 2017"
+REM
+
 cd %~dp0
 call setup-buildtools.cmd
 call build.cmd
diff --git a/tools/build-vs2019.cmd b/tools/build-vs2019.cmd
index b4a39938a3..2fd6dbc59e 100644
--- a/tools/build-vs2019.cmd
+++ b/tools/build-vs2019.cmd
@@ -1,15 +1,13 @@
 REM Build with Visual Studio 2017
-set "VS_TOOLS_VERSION=vs2019"
-set ARCH=Win64
+set "BUILDTOOLS_VERSION=vs2019"
+set ARCH=x64
 if NOT "%1"=="" (
   set ARCH=%1
 )
-if "%ARCH%"=="Win64" (
+if "%ARCH%"=="x64" (
   REM Parameter needed for CMake Visual Studio 2019 generator
   set CMAKE_ARCH=x64
 )
-
-set "CMAKE_GEN=Visual Studio 16 2019"
 cd %~dp0
 call setup-buildtools.cmd
 call build.cmd
diff --git a/tools/build.cmd b/tools/build.cmd
index 14da784661..7558f4efff 100644
--- a/tools/build.cmd
+++ b/tools/build.cmd
@@ -1,6 +1,6 @@
 @echo off
 REM ##########################################################################################
-REM # Build SDK with Visual Studio + CMake + MSBUild or Ninja.                               #
+REM # Build SDK with (msvc or clang) + CMake + (MSBuild or Ninja).                           #
 REM #                                                                                        #
 REM # CMake arguments may be passed as parameters to this script.                            #
 REM # If Visual Studio is not installed, then this script falls back to LLVM-CLang,          #
@@ -10,7 +10,7 @@ REM ############################################################################
 REM #                                                                                        #
 REM # Options passed as environment variables:                                               #
 REM #                                                                                        #
-REM # VS_TOOLS_VERSION   - specify visual studio version. See `vcvars.cmd` for details.      #
+REM # BUILDTOOLS_VERSION - specify build tools version. See `vcvars.cmd` for details.        #
 REM # CMAKE_GEN          - specify CMake generator.                                          #
 REM # VCPKG_ROOT         - path to vcpkg root                                                #
 REM # ARCH               - architecture to build for (default: x64)                          #
@@ -20,36 +20,43 @@ set "PATH=%PATH%;%ProgramFiles%\CMake\bin"
 pushd %~dp0
 setlocal enableextensions
 setlocal enabledelayedexpansion
-if not defined VS_TOOLS_VERSION (
-  set VS_TOOLS_VERSION=vs2019
+if not defined BUILDTOOLS_VERSION (
+  set BUILDTOOLS_VERSION=vs2019
 )
 
 REM ##########################################################################################
 REM Set up CMake generator. Use Ninja if available.
 REM ##########################################################################################
-if not defined CMAKE_GEN (
-  set CMAKE_GEN=Visual Studio 16 2019
-  for /f "tokens=*" %%F in ('where ninja') do (
-    set NINJA=%%F
-  )
-  if defined VCPKG_ROOT (
-    if not defined NINJA (
-      for /f "tokens=*" %%F in ('where /R %VCPKG_ROOT%\vcpkg\downloads\tools ninja') do (
-        set NINJA=%%F
-      )
-      popd
-    )
-  )
+for /f "tokens=*" %%F in ('where ninja') do (
+  set NINJA=%%F
+)
+
+if defined VCPKG_ROOT (
   if not defined NINJA (
-    for /f "tokens=*" %%F in ('where /R %CD%\vcpkg\downloads\tools ninja') do (
+    for /f "tokens=*" %%F in ('where /R %VCPKG_ROOT%\vcpkg\downloads\tools ninja') do (
       set NINJA=%%F
     )
+    popd
   )
-  if defined NINJA (
-    echo Using ninja at !NINJA!
+)
+
+if not defined NINJA (
+  for /f "tokens=*" %%F in ('where /R %CD%\vcpkg\downloads\tools ninja') do (
+    set NINJA=%%F
+  )
+)
+
+if defined NINJA (
+  echo Found ninja: !NINJA!
+  if not defined CMAKE_GEN (
     set CMAKE_GEN=Ninja
   )
 )
+
+if not defined CMAKE_GEN (
+  set CMAKE_GEN=Visual Studio 16 2019
+)
+
 set "ROOT=%~dp0\.."
 if not defined ARCH (
   set ARCH=x64
@@ -80,23 +87,18 @@ REM The following two configurations are built below:
 REM - nostd            - build with OpenTelemetry C++ Template library
 REM - stl              - build with Standard Template Library
 REM ##########################################################################################
-REM Build with nostd implementation. Supported VS_TOOLS_VERSION:
-REM - vs2015 (C++11)
-REM - vs2017 (C++14)
-REM - vs2019 (C++20)
+REM Build with nostd implementation.
 REM ##########################################################################################
 set CONFIG=-DWITH_STL:BOOL=OFF %*
-set "OUTDIR=%ROOT%\out\%VS_TOOLS_VERSION%\nostd"
+set "OUTDIR=%ROOT%\out\%BUILDTOOLS_VERSION%\nostd"
 call :build_config
 
 REM ##########################################################################################
-REM Build with STL implementation (only for vs2017+). Supported VS_TOOLS_VERSION:
-REM - vs2017 (C++14)
-REM - vs2019 (C++20) - optimal config with all OpenTelemetry API classes using STL only.
+REM Build with STL implementation. This option does not yield benefits for vs2015 build.
 REM ##########################################################################################
-if "%VS_TOOLS_VERSION%" neq "vs2015" (
+if "%BUILDTOOLS_VERSION%" neq "vs2015" (
   set CONFIG=-DWITH_STL:BOOL=ON %*
-  set "OUTDIR=%ROOT%\out\%VS_TOOLS_VERSION%\stl"
+  set "OUTDIR=%ROOT%\out\%BUILDTOOLS_VERSION%\stl"
   call :build_config
 )
 
@@ -110,18 +112,36 @@ REM TODO: consider rmdir for clean builds
 if not exist "%OUTDIR%" mkdir "%OUTDIR%"
 cd "%OUTDIR%"
 
-if "!VS_TOOLS_VERSION!" == "vs2019" (
-  REM Prefer ninja if available
-  if "!CMAKE_GEN!" == "Ninja" (
-    call :build_config_ninja
-    exit /b
-  )
-  REM Only latest vs2019 generator supports and requires -A parameter
+REM Prefer ninja if available
+if "!CMAKE_GEN!" == "Ninja" (
+  call :build_config_ninja
+  exit /b
+)
+
+if "!BUILDTOOLS_VERSION!" == "vs2015" (
   cmake -G "!CMAKE_GEN!" -A !ARCH! -DCMAKE_TOOLCHAIN_FILE="!VCPKG_CMAKE!" !CONFIG! "!ROOT!"
-) else (
-  REM Old vs2017 generator does not support -A parameter
-  cmake -G "!CMAKE_GEN!" -DCMAKE_TOOLCHAIN_FILE="!VCPKG_CMAKE!" !CONFIG! "!ROOT!"
+  call :build_msbuild
+  exit /b
 )
+
+if "!BUILDTOOLS_VERSION!" == "vs2017" (
+  cmake -G "!CMAKE_GEN!" -A !ARCH! -DCMAKE_TOOLCHAIN_FILE="!VCPKG_CMAKE!" !CONFIG! "!ROOT!"
+  call :build_msbuild
+  exit /b
+)
+
+if "!BUILDTOOLS_VERSION!" == "vs2019" (
+  cmake -G "!CMAKE_GEN!" -A !ARCH! -DCMAKE_TOOLCHAIN_FILE="!VCPKG_CMAKE!" !CONFIG! "!ROOT!"
+  call :build_msbuild
+  exit /b
+)
+
+REM ##########################################################################################
+REM Exotic CMake generators, like MSYS and MinGW MAY work, but untested
+REM ##########################################################################################
+cmake -G "!CMAKE_GEN!" -DCMAKE_TOOLCHAIN_FILE="!VCPKG_CMAKE!" !CONFIG! "!ROOT!"
+
+:build_msbuild
 set "SOLUTION=%OUTDIR%\opentelemetry-cpp.sln"
 msbuild "%SOLUTION%" /p:Configuration=Release /p:VcpkgEnabled=true
 exit /b
diff --git a/tools/ports/benchmark/portfile.cmake b/tools/ports/benchmark/portfile.cmake
index dba57ab53d..fdb988c538 100644
--- a/tools/ports/benchmark/portfile.cmake
+++ b/tools/ports/benchmark/portfile.cmake
@@ -1,11 +1,7 @@
 if (VCPKG_PLATFORM_TOOLSET STREQUAL "v140")
-  # set(CMAKE_C_COMPILER_WORKS 1)
-  # set(CMAKE_CXX_COMPILER_WORKS 1)
   set(CMAKE_C_COMPILER cl.exe)
   set(CMAKE_CXX_COMPILER cl.exe)
   set(MSVC_TOOLSET_VERSION 140)
-  # set(VCPKG_VISUAL_STUDIO_PATH "C:\\Program Files (x86)\\Microsoft Visual Studio 14.0")
-  # set(VCPKG_PLATFORM_TOOLSET v140)
 else()
   # Make sure vs2019 compiled binaries are compat with vs2017
   set(VCPKG_CXX_FLAGS "/Zc:__cplusplus /d2FH4-")
diff --git a/tools/setup-buildtools.cmd b/tools/setup-buildtools.cmd
index fd31eb21fd..956c8ddfe4 100644
--- a/tools/setup-buildtools.cmd
+++ b/tools/setup-buildtools.cmd
@@ -1,8 +1,12 @@
 @echo off
 setlocal enableextensions
 setlocal enabledelayedexpansion
-set "PATH=%ProgramFiles%\CMake\bin;%~dp0;%~dp0vcpkg;%ProgramData%\chocolatey\bin;%PATH%"
-if "%VCPKG_ROOT%" NEQ "" set "PATH=%VCPKG_ROOT%;%PATH%"
+set "PATH=%ProgramFiles%\CMake\bin;%~dp0;%ProgramData%\chocolatey\bin;%PATH%"
+if defined VCPKG_ROOT (
+  set "PATH=%VCPKG_ROOT%;%PATH%"
+) else (
+  set "PATH=%~dp0vcpkg;%PATH%"
+)
 pushd %~dp0
 
 net session >nul 2>&1
@@ -22,11 +26,13 @@ if %errorLevel% == 0 (
   echo Running without Administrative privilege...
 )
 
-REM Print current Visual Studio installations detected
-where /Q vswhere
-if %ERRORLEVEL% == 0 (
-  echo Visual Studio installations detected:
-  vswhere -property installationPath
+if not defined BUILDTOOLS_VERSION (
+  REM Print current Visual Studio installations detected
+  where /Q vswhere
+  if %ERRORLEVEL% == 0 (
+    echo Visual Studio installations detected:
+    vswhere -property installationPath
+  )
 )
 
 REM This script allows to pass architecture in ARCH env var
diff --git a/tools/vcvars.cmd b/tools/vcvars.cmd
index 69308778a7..94f5cca95a 100644
--- a/tools/vcvars.cmd
+++ b/tools/vcvars.cmd
@@ -1,7 +1,7 @@
 @echo off
 REM +-------------------------------------------------------------------+
-REM | Autodetect and set up the build environment for Visual Studio.    |
-REM | Visual Studio version may be specified as 1st argument.           |
+REM | Autodetect and set up the build environment.                      |
+REM | Build Tools version may be specified as 1st argument.             |
 REM +-------------------------------------------------------------------+
 REM | Description                             | Argument value          |
 REM +-----------------------------------------+-------------------------+
@@ -18,6 +18,12 @@ REM | Visual Studio 2017 Community            | vs2017_community        |
 REM | Visual Studio 2017 Build Tools (no IDE) | vs2017_buildtools       |
 REM |                                         |                         |
 REM | Visual Studio 2015 Build Tools (no IDE) | vs2015                  |
+REM |                                         |                         |
+REM | LLVM Clang (any version)                | clang                   |
+REM | LLVM Clang 9                            | clang-9                 |
+REM | LLVM Clang 10                           | clang-10                |
+REM | LLVM Clang 11                           | clang-11                |
+REM | LLVM Clang 11                           | clang-12                |
 REM +-----------------------------------------+-------------------------+
 set "VSCMD_START_DIR=%CD%"
 
@@ -29,8 +35,8 @@ if "%1" neq "" (
   goto %1
 )
 
-if defined VS_TOOLS_VERSION (
-  goto %VS_TOOLS_VERSION%
+if defined BUILDTOOLS_VERSION (
+  goto %BUILDTOOLS_VERSION%
 )
 
 :vs2019
@@ -100,10 +106,10 @@ if exist %TOOLS_VS2017% (
 )
 
 :vs2015
-set TOOLS_VS2015="%ProgramFiles(x86)%\Microsoft Visual Studio 14.0\VC\bin\vcvarsall.bat"
+set TOOLS_VS2015="%ProgramFiles(x86)%\Microsoft Visual Studio 14.0\VC\vcvarsall.bat"
 if exist %TOOLS_VS2015% (
   echo Building with vs2015 BuildTools...
-  call %TOOLS_VS2015% %ARCH%
+  call %TOOLS_VS2015% %ARCH% %WINSDK_VERSION%
   set "VCPKG_VISUAL_STUDIO_PATH=%ProgramFiles(x86)%\Microsoft Visual Studio 14.0"
   set VCPKG_PLATFORM_TOOLSET=v140
   goto tools_configured
@@ -115,4 +121,38 @@ REM is not set up by checking TOOLS_VS_NOTFOUND
 set TOOLS_VS_NOTFOUND=1
 exit /b 0
 
+REM +-------------------------------------------------------------------+
+REM | There is no auto-detection of LLVM Clang version.                 |
+REM | LLVM Clang of any version is installed in the same directory      |
+REM | at %ProgramFiles%\LLVM\bin . Developers choose their own custom   |
+REM | layout for installing multiple clang toolchains side-by-side.     |
+REM |                                                                   |
+REM | Example layout (merely a guideline, layout could differ):         |
+REM |                                                                   |
+REM | %ProgramFiles%\LLVM-9\bin                                         |
+REM | %ProgramFiles%\LLVM-10\bin                                        |
+REM | %ProgramFiles%\LLVM-11\bin                                        |
+REM | %ProgramFiles%\LLVM-12\bin                                        |
+REM +-------------------------------------------------------------------+
+REM
+REM ## Example 1: use clang-10 located in LLVM-10 directory:
+REM set BUILDTOOLS_VERSION=clang-10
+REM set "PATH=%ProgramFiles%\LLVM-10\bin;%PATH%"
+REM tools\build.cmd
+REM
+REM ## Example 2: use whatever clang located in LLVM directory:
+REM set BUILDTOOLS_VERSION=clang
+REM set "PATH=%ProgramFiles%\LLVM\bin;%PATH%"
+REM tools\build.cmd
+REM
+REM BUILDTOOLS_VERSION determines the output directory location.
+REM Store build artifacts produced by different toolchains -
+REM side-by-side, each in its own separate output directory.
+REM
+:clang
+:clang-9
+:clang-10
+:clang-11
+:clang-12
+
 :tools_configured